1. Field of the Invention
The present invention relates to a method, system and program for providing direct file access to a client in a data management system.
2. Description of the Related Art
A source code management (SCM) system manages the source code of software projects, especially multi-programmer projects, tracking revisions to the entire software system and making all product releases consistent. When multiple programmers work on the same project, one of the primary functions of an SCM system is to provide some form of synchronization control to prevent the same version of a source file from being modified simultaneously by more than one programmer. Even when programmers or programming teams work in geographical isolation from each other, SCM systems are capable of merging individual modifications to files and groups of files without causing conflicts.
Prior art SCM systems maintain a record of versions of files and other internal components of one or more software products. A record is typically kept with each set of changes of what the changes are, why the changes were made, when the changes were made and who made the changes. Older versions can typically be recovered, and different versions can be maintained simultaneously. Some SCM systems also facilitate the tracking of software product builds that encompass various phases such as compiling, assembling, linking and so on. More advanced SCM systems can also enforce additional process management mechanisms including access control, security, approval control for modifying source code and so on. Typical SCM systems known in the art include IBM Configuration Management and Version Control (CMVC), Concurrent Versions System (CVS), Revision Control System (RCS), Source Code Control System (SCCS).
To provide an illustrative example, consider a software product being built by several teams of programmers working in geographical isolation from each other. The source files that go into building the software product are shared among the programming teams. During the course of development of the software product the files may have to be changed several times, i.e., each file may have many versions. In addition, often multiple programmers may wish to make changes to the same source code file at the same time. The changes to the files must be made without causing any conflicts or disruptions to the process of building the software product. Typically, SCM systems ensure this by providing for check-in and check-out control of source code files. When one programmer has checked-out a file to change the content the other programmers cannot make any changes to the file. In other words, when a file is checked-out, the file is locked. Other programmers can of course view the contents of the file with appropriate authority typically provided by the SCM administrator or the SCM delegate. In a common situation only after the source code of the file has been changed and a new version of the file checked-in can the other programmers check-out the file again. When a source file has been checked-out by one programmer, other programmers wanting to view the content of the file can extract the file. If a first programmer locks a file, no other programmer can make changes to the file until the first programmer has unlocked the file.
In typical prior art SCM systems, the process of limiting and auditing changes to files through the mechanism of checking files in and out is usually done by accessing a single central server, i.e. the SCM server. A storage location referred to as “file storage” is connected to, in proximity, and controlled by the SCM server. The programmers access the SCM server via SCM clients. All communications to access files from an SCM client, such as check-out, check-in, extract etc. must flow between the SCM client and the SCM server. In other words, existing SCM systems require the SCM client to access the correct version of source files only through communication with the SCM server. When an SCM client wants to access a file, the SCM client sends a request to the SCM server. The request specifies the name of the file. The name of the file is referred to as “filename”. The SCM server locates the file in the file storage and controls the SCM client access to the file. If the request is for a check-out or extract the SCM server secures the file from the file storage and transmits the file to the SCM client. If the request is for a check-in, the SCM server receives the file from the SCM client and creates a new version of the file in the file storage. Since files are often large, the time to transmit and receive files is significant when compared to other activities within an SCM system. In particular, when the SCM clients are geographically dispersed and the SCM server is located across a Wide Area Network, the file access times between the SCM clients and server can be significant.